In a representative glass fiber manufacturing facility, typically 10-20 wt % of the processed glass material is not converted to final product and is rejected as industrial by-product or waste and sent for disposal to a landfill. This rejected material represents a substantial cost to the industry and also generates a consequent detrimental impact on the environment. While the rejected by-product referred to may have widely varying physical form, ranging from thick fiber bundles to partially fused fiber agglomerates and shot, it is evident from chemical analyses of various samples recovered at different times, that the material still has a substantially constant chemical and mineralogical make-up. Thus, unlike wastes from many other industrial processes which typically have widely varying chemical and mineralogical properties, the waste from the glass fiber manufacturing process is very consistent in composition and still benefits from the stringent engineering quality control applied to the glass-making process itself. This consistency is a major advantage to any potential utilization of the glass fiber manufacturing waste.
More specifically, the glass formulations of great relevance to this invention are those of low alkali calcia-alumina-silica compositions (CaO—Al2O3—SiO2 or “CAS”) typically used for commercial glass fiber manufactured to comply with ASTM D-578. These formulations are given in Table 1. The compositions are vitreous and by virtue of their components have very low levels of discolorants. These compositions are expressed conventionally in terms of the element oxide and are not meant to imply that the oxides, crystalline or otherwise, are present as distinct compounds in the amorphous glasses.
TABLE 1Composition RangeComponent (Element Oxide)(% by Weight)Silicon dioxide, SiO252–62Aluminum oxide, Al2O312–16Iron oxide, Fe2O30.05–0.8 Calcium oxide, CaO16–25Magnesium oxide, MgO0–5Sodium oxide + potassium oxide (Na2O + K2O)0–2Boron oxide, B2O3 0–10Titanium dioxide, TiO2  0–1.5Fluorine, F20–1Mineralogical Composition (XRD)Amorphous (glassy)
Several features are immediately evident from inspection of the data in Table 1. First, the general chemical and mineralogical composition of the glass fiber material is very similar to amorphous (glassy) calcium alumino-silicate materials, such as blast-furnace slag and Class C fly ash, that are commonly used as cementitious or pozzolanic admixtures in portland cement concrete; second, the alkali (Na2O+K2O) content of the glass is very low (0 to 2%); and third, with their inherently low iron contents (0.05 to 0.8%), the glasses have little or no color. Low alkali content and chemical consistency differentiates the glass fiber manufacturing waste from post consumer waste glass, for example container bottles and flat glass, that have widely varying chemical composition, generally high alkali content, and in the case of container/bottle glass are highly colored.